Elsewhere on today's program, we began hearing about Steve Inskeep road trip along the U.S./Mexico border. His team set off from the Gulf of Mexico and headed west towards the Pacific, seeking stories of people, goods and culture that cross the border.

STEVE INSKEEP, HOST:

This road trip also let us into history. On our way to the border, we found a place to see how the dividing line came to be drawn just where it is. It is an amazing cloudless day in San Antonio, Texas, and just across the street from us here is a low stone wall, part of the parameter of The Alamo. American settlers fought a battle at The Alamo in 1836.

Back then, San Antonio was part of the Mexican state of Texas or Tejas. The American border was in a totally different place. Louisiana was a border state, even California was Mexican soil. The Texas settlers were fighting for independence from Mexico, but all were killed as we could see inside the gift shop. We visited The Alamo with a Texas historian, Frank de la Teja. What are we looking at here?

FRANK DE LA TEJA: Ah, the Diorama.

INSKEEP: Of the battle of The Alamo.

TEJA: The Diorama of the battle of The Alamo.

INSKEEP: Thousands of little tiny Mexican soldiers charging the wall.

TEJA: That's right. And we are right over here.

INSKEEP: The Diorama really drew in visiting children.

UNIDENTIFIED CHILD: Look, this guy died all the way over here.

INSKEEP: One doomed defender is Davy Crockett, another is Jim Bowie. Frank de la Teja was impressed.

TEJA: It's a good Diorama. It's a good way to explain things to people because it certainly - where we are does not look that way today.

INSKEEP: He says that because most of The Alamo is gone today. The outer walls of this former Catholic mission were torn down long ago. Newer streets and buildings rest on their foundations. The main surviving Alamo building is the old white chapel with its carved stone columns flanking the door.

TEJA: It is an island of the 18th century in essentially a 20th century city.

INSKEEP: The modern city has literally been built on its past. Texas, like the whole American southwest was once claimed by the Spanish empire. Then, Mexico won its independence in 1821, a vast new nation bankrupted by its uprising against Spain. Sitting by The Alamo chapel, Frank de la Teja told us what happened next. Mexico was desperate to settle and control its sparsely populated war-torn province of Texas.

Soon, officials received a visitor from the neighboring United States.

TEJA: They see the opportunity that is offered by a man named Moses Austin who offers to bring 300 Catholic American families to settle in Texas. They see that as the opening to progress.

INSKEEP: Mexican residents of Texas, Tejanos, welcomed American settlers at first. The Americans swore to become loyal Mexicans. Then, more Americans came, and more. And the Mexicans in Texas began to worry.

TEJA: And one of the complaints that the Tejanos themselves have, we need troops up here. We need to be able to defend the border. There's nothing to stop Anglo-Americans and Indians from invading Texas and doing what they want and illegally establishing themselves here. So we need the government.

INSKEEP: Were they right?

TEJA: They were right, as it turned out, because Americans began to arrive legitimately, but also many squatters, many people who just crossed the border. Some of these...

INSKEEP: Illegal aliens is what we would call them these days.

TEJA: Illegal aliens, undocumented westward-moving farmers.

INSKEEP: So we go through the 1820s, 1830s. Thousands of Americans have showed up here.

TEJA: Absolutely.

INSKEEP: Many of them illegally.

TEJA: Overwhelming the local population. One Mexican official traveling through and making a report on the conditions in early 1830s Texas says that all these Americans are walking with their constitution in their back pocket, and if you say anything to them, they pull it out and tell you that these are their rights.

INSKEEP: Believe that (unintelligible)

TEJA: Exactly. So many of them, after they arrive, are not willing to make themselves Mexican.

INSKEEP: Mexico had asked the settlers for allegiance to their new country, but these settlers in the 1830s had their own concept of citizenship. Frank de la Teja says authorities tried to control the flood of newcomers. Mexico passed a law to restrict immigration and sent soldiers into Texas. It was too late. By 1835, the newcomers began a war for independence from Mexico. So if you had to put in a sentence the Mexican narrative and the American narrative of what was happening in the Texas War of Independence, what would the sentence for each side be?

TEJA: Well, the Mexican narrative is based on essentially what they call piracy and...

INSKEEP: Just like taking a ship at sea.

TEJA: Just like taking a ship at sea...

INSKEEP: They're taking a province.

TEJA: They're trying to steal Texas away from its legitimate owner. It's an act of piracy and therefore there should be no mercy shown to any of these people, so...

INSKEEP: And what was the American narrative?

TEJA: And the American narrative is that Mexico is what we would say in modern parlance, a failed state, a tyranny.

INSKEEP: The Americans believed a weak central government was failing to keep its promises to protect their settlements.

TEJA: And in breaching that agreement, they had no right to retain Texas.

INSKEEP: When I listen to you, it sounds like you accept a little bit of truth in each of those narratives.

TEJA: Absolutely. History is messy.

INSKEEP: The rebellious Texas settlers included William Barrett Travis who originally came to Texas as an undocumented immigrant. He became the co-commander at The Alamo and refused to surrender. The Mexican army slaughtered his troops, but weeks later, Texas forces under Sam Houston devastated the Mexican army.

Texas became independent and then an American state in 1845. A dispute over the Texas borderline lead to the United States war with Mexico, in which the U.S. captured California and the whole southwest. That's why the border is where it is and it all started with that American migration to Texas. I'm maybe being a little provocative in describing some of the people who came to Texas as illegal aliens or illegal immigrants, although it seems like it was literally true.

TEJA: It's literally true.

INSKEEP: But that would then raise another question in people's minds. Mexico had reason to fear illegal immigration. They ended up seeing the country dismembered. Is there any lesson for the United States today when it thinks about immigration?

TEJA: Well, it's different. For one thing, although the Mexican-American population in Texas is growing and in the next 20, 30 years it'll probably be the majority population in Texas, it is not a Mexican population. It's a Mexican-American population. Mexicans who are crossing over are crossing over to the opportunities that exist here, American opportunities.

They want American jobs. They want American education. They want American things, if you will, the material culture of America. So they're coming here to become Americans.

INSKEEP: And the borderland is where these two countries meet, two nations whose histories have always been tangled together. Frank de la Teja says you can feel that when you travel to the modern day border.

TEJA: It's really a significantly different place from either the interior of Mexico or the interior of the United States. And it begins right about here, right in San Antonio, from here going south and going west, it's a different cultural zone.

INSKEEP: That's the zone we're passing through on NPR News as we drive the U.S./Mexico borderland from one end to the other. Transcript provided by NPR, Copyright NPR.